During oil and gas well drilling operations, strings of pipe are used to both drill the well and line the drilled hole with conduit. The pipe is made up of discrete sections of pipe, each approximately 40 ft in length or in stands of approximately 90 feet in length. These sections of pipe are made up to one another at the rig via locking and sealing connections, typically threads, and then lowered into the well. In many cases, it is necessary to turn the connected sections of pipe while lowering them into the well, either to support a drilling activity or to help keep the pipe from becoming stuck in the well.
In recent years, the rigs used to drill wells and install pipe have been modified to automate much of these activities that previously involved men working on the rig floors exposed to potentially dangerous conditions. Many modern rigs now have automated spiders at the rig floor to support the sections of pipe already installed in the well; top drives with pipe handling tools for gripping sections of pipe, lifting them and turning them; and other ancillary equipment to assist in the handling and manipulation of the pipe during drilling and running operations.
Pipe handling tools mounted to the top drive typically used a quill connected by threads to the top drive through which both lifting forces and torsional forces could be selectively applied to pipe. Surrounding the quill typically was a set of slips that could be moved along a tapered surface into an engaging connection with the pipe. The tapered surface could either be an internally tapered surface or an externally tapered surface, depending on whether internal gripping or external gripping is desired. An actuator is required to move the slips between the engaging connection with the pipe and a disengaged position. Typically, the actuator is made up of a number of pneumatic or hydraulic cylinders that are mounted around the quill and connected to the slips to effect movement of the slips from a released position to an engaged position with the pipe. Alternatively, a pneumatic or hydraulic mono-cylinder could be mounted around the quill using multiple sleeves and connected to the slips to effect movement of the slips.